Transceiver having switch controlled frequency compensator



July 18, 1950 P. F. e; HOLST ET AL 2,515,225

TRANSCEIVER HAVING SWITCH CONTROLLED FREQUENCY COMPENSATOR Filed Dec. 50, 1944 I5 Sheets-Sheet 1 ATTORN EY y 1950 P F G HOLST ETAL 2,515,225

TRANSCEIVER HA VING SWITCH CONTROLLED FREQUENCY COMPENSATOR Filed Dec. 30, 1944 3 Sheets-Sheet 2 INVENTORS P404 F. 6. 6 0457. BZYOPE/V F.A /e,m aaa 'A'T'roRNEY Patented July 18, 1950 UNI ED -S.;TATES TRANSCEIVER HAVING J SWITCH con};- TaoLLEDj FREQUENCY coMrENsA'roR" Paul F. G. Holst-and Loren" Kirkwoodgtflaklym:

' N. 3;, assignors to Radio Corporation of ica; a corporation of Delaware:

Amer- Application December 30, 1944, Serial'N'o. 570,670

This invention relates to improvements in radio transceivers; and particularly to ultra high ire-- quency-transcei-vers employing cavity tuned circuits-and operatingin a frequency range of the order of 1000 'megacycle's and higher.

The termtransceiveris used herein to designate radio apparatus which can alternately transmit orreceive radio waves by means of the same: electrondischarge device' circuit whose function is changed f'orthe 1 two diiierent'condil andMacLean, which describ'es such a transceiver.

In: the-system of ithis copendingapplication, a switchis-used to change from the receiving'condition to =-the transmitting condition, and automatic'means is provid'edfor compensating for the unavoidable change in the oscillator frequency-ofthe cavity tuned circuit when the system is ch'anged from ethe receiving condition to the-transmittingcondition. The-automatic frequency-compensator; in its essentials, comprises assolenoid controlling aplug adapted to enter 8 Claims. (Cl: 250 -13) the cavity in a suitablelocatibn; A relay is=employed'iunder controlofi the switch to enable the system, remotely controlled, to change from the receiving:- toitheatransmitting condition.

Characteristics. ofthes particular system just described are'ithat theif'requen'cy of reception is adjusted. tozonesiderof the transmitter frequency only andtherefore thetransmitter frequencies at any two transceivers inrcommunication with each other -mustxb'e set almost exactly alike; and the vacuunmtubesmsed must not onlybe of the same typeebut' I they must changeavery much in like manner with changer-in operating conditions; It will thuszbe seen thewcomponents'of the equipment ands its ;ad-justments. arerather critical.

The present invention concerns improvements in;;:the foregoing atype oftiultra high frequency transceiver :whiclrutilizes a cavity tuned circuit and; an; automatic jfrequencyicompensation feature. Some of the objects: of: the present inventionaare. (1)-- torprovide artransceiver I which permits a ma'ximum degree or flexibility during usages ,(2): togproride'fat-transceiver which is so adj ted:-t;.that-:,- reception is possible? over i a desired:ran ewnnbotlr;sidesaof:the transmitter frequency; and (toprovide 1 a transceiverwhich is:more* compactplighter in-weight;and rnore eco nomical to use than the foregoing described sys- .a A feature of the present invention-"comprises the insulation plug enclosinga metal rodg'andtiie associated" mechanicalelements employed-for changingthe frequency 0f the cavityresonator. Another feature-is the arrangement which' eri ables a 'singlekrelay -to' efict frequency compensation, and also-switch the-circuit connections for changing-the operation of the transceiver from the receive to the transmitconditions 5 Inthe system of the invention, the same -li'gl ithouseoscillator tube -'is used b'otlr as an anode modulated transmltti ng oscillator and as a superregenerative detector. When two-such transceiver: units are' in communicati'on with ea ch other, it is necessary tli'at the receivingirequency of each unit be= adjusted to the transmitter frequencyof-the other unit:- Because each transceiver wil' shift it'sfrequency slightly when the unit changes frorn the transmission condition 5 to ithe reception conditien; and vice ve'rsa} and since neither the transmitter nor the 1 receiver frequency will' be absolutel y constant duringop era-tion; it i's-essential to provide apparatus of this typeiwitlr somefarra'ngement which will permit tlie operators to maintain =the-transceivers tuned ztoeach other? Tl'iepperatorat the-transceiver un it -wh ich :is' at thatm0ment"'in* the-receiving cond-itionis the logicalmerson to determine whether or not thetransmitterand" receiver frefquencies' are *alike or matched; and for this rearson lie-should be-able to adjust the receiverirequency-to the incoming transmitter 'freque'ncy radiated-from the remote. transceiver. It is inrportant; however; that-the adj ustment'of the receiver tuning shouldnot alter the frequency" fof transmission atthe same transceiver," sinceotherwise; the. operators 1 at "the different transceivers might haveto.'hunt fo'r-eachj othen. The present invention l enablessthe transceiver to? 0perate at laiixe'd transmitter frequencywhilesthe frequency ofreceptionsrnay-lbe :changedmanually over v-a narrow'r frequency range: located ozrboth sideshoftthe transmittal-frequency. 1

A more detailed descriptioncofrthe invention follows inconjunctionwwithr drawings; =--.wherein 1 Figzg-l illustrates; in section; certain rmechantcal details of ther: ultra whigh frequency vtrans ceiverisystem of'?-th'e-'invention; v 5 Fig lit-illustrates in perspective-andwith=mor cert-r111 the mechanicalfeatures -of-the relay erectresonant frequency of the coaxial line.

.a resonating coaxial line.

ing the control of the frequency compensation and the switching of the circuits;

Fig. 2 schematically illustrates a transceiver circuit in which the apparatus of Fig. 1 is used;

Fig. 3 is a graph given in explanation of the operation of the frequency adjusting mechanism of the invention;

Figs. 4a and 4b show the limits of movement of the metallic rod adapted for movement between the side walls of the cavity resonator, for the receiving condition; and

Figs. 4c and 441 show the limits of movement of the metallic rod adapted for movement between the side walls of the cavity resonator, for the transmitting condition.

The system of Fig. 1 shows the mechanical details of the ultra high frequency oscillator circuit employing the vacuum tube T and the associated cavity resonator I. Resonator I has side walls A and B. The oscillator vacuum tube .isof the lighthouse type. wherein the grid and anode connections protrude through the glass en- .velope in the form of parallel metallic rings spaced from one another along the length of the tube. These metallic rings or discs connect with the cavity resonator I on opposite sides of the cavity, as shown. The grid ring is labeled 6 and makes contact with one wall of the cavity resonator through spring contacts 22 while the anode ring I makes contact with the opposite wall of the cavity resonator. The cavity resonator is provided, at the wall which accommodates the anode ring I, with a metallic plate 2I apertured at the center. Metallic plate 2| is capacitively coupled to the rest of the wall of the cavity resonator through the mica spacer I2. The condenser formedbetween the metallic ring 21, to

which the anode ring is directly connected, and the adjacent wall of the cavity resonator is a low impedance path for energy of the operating frequency, and thus it will be seen that the anode of the lighthouse tube is by-passed to the wall A of the cavity resonator for radio frequency energy. The oscillator tube T includes a metallic shell 5 and a tube socket 4. A suitable lighthouse tube of the type shown in the drawing, mentioned by, way of example only, is the RCA type 446B 'triode. on base 4 by means of a rod 9 which forces the grid and plate rings 6 and I, respectively, against The tube T is held in place by pressure their respective contacts in the cavity resonator I.

The grid-cathode circuit of the oscillator includes a tunable coaxial line having an inner hollow conductor 3 and an outer hollow conductor 3', both conductors being connected together at one end by a metallic ring 5| and a metallic end outer conductor 3' is preferably of round configuration for practical reasons, although if desired it may be square in form. Tuning of the coaxial resonator is achieved by means of capacity "adjustments I and III which varies the capacity across the coaxial line and thus changes the The metallic shell is capacitively coupled to the cathode by means .of a mica condenser built into .the tube, and hence it will be obvious that the control grid and the cathode are connected by The cathode line is also provided with shortingsprings I! to prevent this line from resonating at an undesired low frequency without harming its usage as a threequarter wavelength line.

The dimensions of cavity resonator I are such that the entire cavity is resonant at the desired frequency, with a standing wave one wavelength long in its short dimension. The frequency of the cavity resonator may be varied by means of adjustable spring end pieces which terminate the cavity in its long dimension and are designed to be moved a desired amount in the direction of the arrows, as shown in Fig. 1a, for permitting initial setting of the cavity resonator frequency.

The output circuit is in the form of a loop 45 within the interior of the cavity resonator, preferably entering the resonator on the same side as the tuning mechanism. This loop extends by way of a coaxial line 46 to a suitable antenna. Feedback energy to sustain the oscillation is obtained from the capacity coupling between the plate and cathode within the tube itself.

It will thus be seen that the frequency at which the 4463 lighthouse tube T oscillates is determined principally by the adjustment of the cavity resonator I, while the tendency to oscillate or the amount of feedback is determined by the tuning of the cathode coaxial line. If the latter adjustment remains fixed, it is therefore possible to change the oscillator frequency within a narrow frequency range by adjusting the resonator I. The cavity resonator I is tuned by its end pieces 2, and in addition, it is provided with a capacity tuning adjustment which forms part of the auto.- matic frequency compensation and receiver tuning arrangement now to be described.

The automatic frequency compensator in its essentials includes a relay I5 in the form of a solenoid controlling the movement of a plug I9, by way of magnetic armature I8. Relay I5: also controls a group of contacts 50 for switching the transceiver from the receiving condition to the transmitting condition, as shown in more detail in Fig. 2. Plug I9 is made of insulation material, such as styrol, and surrounds a small metallic rod 20, such as aluminum. The length of the rod 20 is slightly longer than the distance between the two bushings 44. The plug I9 is inserted in the cavity I and extends across both side walls thereof through bushings 44, at a location where the voltage gradient. across the cavity i large. One end of plug I9 issecured to a leaf spring 23, in turn connected through rocker arm 24, to an arm 25 for actuating the rocker arm. In the receiving position of the system, the spring 26 exerts pressure on rocker arm 24 and leaf spring 23 to seat the plug I9 in the position shown in the drawing against the receiving tuning knob 21, the latter in .turn threadedly engaging a support 28 mounted on the outside of the wall A of the cavity resonator. When'the relay I5 is energized, which occurs during the transmitting condition of the system, the armature I8 will engage the actuating arm 25, thus turning rocker arm 24 and causing the leaf spring 23 to pull the plug I9 to the right against the opposing force of restoring spring 26. It willthus be seen that slidable plug I9 is rapidly movable under control of the relay I5; and that there is no obstacle to prevent the relatively free movement of the plug when the relay is actuated. I

A stop 29. isprovided for limiting the motion of the styrol rod I9 to the right by virtue of the flange I6. This stop'controls the transmitter frequency and is fixedly set at one position during' the alignment of the transceiver. A tuning zgsnsgeas knobm la furnishes-a; stopnfor :Iimiting-thamotion of: 31183 styrolirod 11 931201171163 left-1. ThiS I-StOPJ-GOIIL- trolszthe; receiven frequency; andis manually adijustable by. theroperatonofgtheequipment;

The. position;.ofiitheistyrolz plug; [9.2 with; its encloseda' shorter,- aluminum rod determines. the frequency of theacavity: resonator; I); ignoring. for thei'momente thecadjustment whicl'ncani'bee made byatlie sliding.- end piecesi.2..:. Movement. of this plug: LS3 effec.ts:.a.- capacity tuningt adjustment of thexcavitys-zl. Thecapacity addediacross the cavity resonator. will hez a. maximum...when..the; rod: 211 isrlocatedr uidistant; between. the etwlo bushings 44; and the added capacity wilhhe aminimum whemthastyrolpluge 1.9 is moved. toi-v either side smthat-tnos part ;of.: thee-aluminum; roctis located withim theicavity. Thezeffectrof moving the aluminum .rodrthrouglnthe; cavity 15110111 10118 side toi thezotheitisztabulatedcas follower.

Location of 'rod'20 Capacity g g g gggig i Minimum; Maximum.

LGr-eater their: (a)- Less thanj(c).-.x

(qyOutside; cavityonside A Lower than (b)'::Inside cavityon-side a). A- H1gh er. than .(c).

(C)',H1side cavitylocate'd" Maximum ltlinirnum.

symmetricallywithrespeot-tothe: q 7 sides of the cavity. g

(iiX-lnsidecavityonsidea Less than-(c) Highcrthan-(c).

B More thank) Lower than (e). I

(0) Outside cavity on sidevB;

Whemthe aluminum rod 2ll ismoved through the cavity I; it will'be noted' that cavity. tuning frequency-passes twicerthroug-h the same fre- 'theefstyrol. plug; 1.9;.- .to: rest:;against the stop 2''! when\theiequipmentjsereceiving? and. against the stop'atfiiwhen transmitting. I

Thhnadiustment in; positioncohthe aluminum rodgzflj inithesdesign. and-operation of. the tran ceiver: of, the inventiommaybe better underslleodi-flionriallinspection.of, the: curve of Fig. 3

impuniunction. with-the views of- Figs. lato M. In drawing the..curve;o fFig.. 3, it has been as- .sumedthai ii' he'transceiveris designed to operate over-,a.rangev ofv approximately. 2 100 to 2300 megacycles,. with theoperating' frequency. determined principally by-the settingofthe sliding end pieces 2. Minor adjustments in frequency may be. made by. changing. the settingofthe rod. 20. Forv a fixedsettingpf. the endfpieces 2, the position of rodj' ll' injfig, 4a shows the setting,.for the. lower frequency limit for reception. This position may correspondjto 2180 megacycles. The position of rod i'njFig'. 4b shows the upper frequency limit-for reception. This position may correspond to 2220 megacycles. "The" two positions of Figs-.40; anddb correspond to the two extreme positions-- of the receivertuningknob 2-72 The movement between these two extreme positions is-iixedzdn the. mchanical design. Theposition :of rod. 20 4c.a;sliows the' setting for the at the center of the frequency rangeyis that the transmitter frequency unfortunately, may drift in either direction from the. mid. frequencyzof 2200 megacycles, and it is; desired that the remote transceiver still, be able to receive this changed or drifting transmitter frequency; This permits maximum flexibility in using the transceiver of the invention. a

An inspection of Figs.=la and will show. that the center of the rod 20 is displaced from the center line of the: cavity resonator for the lowest frequencies of operation, inboth; the" receiving andtransmittingpositions. This is" because it is desired that the frequency should change or progress in only one direction with rotation of the tuning knob and" notreverse itself.

In using: the transceiver of the invention, the operator can change only the receiving tuning adjustment by means offtuning knobal. The transmitting tuning adjustment isfixed, when theapparatus is set up andrthe. operator cannot makeany changeain this adjustment without removing the? chassis from its cover.

A: suitable transceiving system employing the apparatus of Fig. 1. is illustrated in Fig.2. The system of Fig. 2 employs the ultra high 'frequency'oscil'latorT, both as a. transmitting oscillator andias a super-regenerative detector: The same reference, numeralssemployed in 1 have been used-in; Fig. 2 to identify the same parts. The cavity resonator tuner'unit is labeled I, the lighthouse tube is labeled'T, the relay is labeled l5; A squelch oscillatortll; which may be' an RCA 6C4 triod'e operating on a'frequency of'approximately 100 kilocycles when the transceiver -is.;o-perating as. a receiver, servesto anode modulate-the ultra highfrequencyoscillator Tat a 100 kilocycle rate for super-regenerative action. The relay I 5 serves toconditionthe system for either receiving or transmitting undercontrol of the switch 8.. Vacuum tubeslfl and 32, which may also be RCA 604' tubes; comprise two stages of audio frequency-amplification having an inputtransformer 33 and an output transformer -34.

In'the'operation of the-transceiver of Fig. 2, the-system as shown in the drawing is in the receiving condition, in which case the contacts will beas indicated in the drawing and-the relay I5 unenergized; Signals picked up by the antenna I00 are coupled to the cavity resonator I, which in conjunction with the lighthouse tube 'I functions as a super-regenerative detector. The plate or anode P ofthetube 'T' is connected through relayswitch contacts 59 and 60 to 'the tap of thesecondary of "the input transformer 33'. The low side of" the secondary windingis connected to-the-anodeof the squelchoscillator tube.3ll, whereby thekilocycleanode modulation of the oscillator tubeTis effected. The

audio voltage which is generated "in; the superregenerative detector T isimpressed across the part of the' secondary winding of 'input transformer 3.3; which is connected;between:'the anode of the squelch oscillator-$0 and the" oscillatorT.

The audio voltage is steppedup bys thetransformer. action and is im'pressed' 'across'theyolume will during transmission couple the control 40. A portion of the audio voltage is obtained at the arm of 40 and is fed through thecontacts 53 and 52 in the relay switch to the grid of thefirst audio amplifier tube 3!. This tube amplifies the audiovoltage and through suitable coupling means feeds the amplified audio voltage .to the control grid of the power amplifier 32. This tube further amplifies the audio voltage and through the output transformer 34 actuates theheadset 1|]. V

The squelch oscillator 30 is of the type com- 'monly known as a Hartley'oscillator, and oper- The relay actuating coil [5 is permanently connected at one end of the coil to the 6 volt direct current filament supply voltage, so that when the other end of the coil is connected to ground through contacts C and D, the relay will be actuated and switch the transceiver to its transmit condition. The 'relayperforms two functions: First, it changes the relay switch so that it contacts the other set of terminals and second, it moves the tuning plug within the cavity asexplained above. a

Depressing the button on the microphone also connects the free end of the microphone to ground. This action completes the microphone circuit, since the other side of the microphone is permanently connected to one side of the primary winding on the input transformer 33. Pclarizing voltage for the microphone is provided from the 6 volts direct current filament supply through contacts 64 and 62 on the relay switch and the filter 14, 15. The audio voltages are therefore connected to the primary of the input transformer 33, in which they are stepped up and impressed across the modulation depth control I6. Part of this voltage is'fed from the arm of the modulation depth control 16 through contacts 53 and 5| on the relay switch to the control grid of the audio amplifier 3|, in which the signal is amplified and coupled to the control grid of thepower amplifier 32. The anodes of the power amplifier 32 and the oscillator T are connected in parallel through the contacts 60 and 58 on the relay switch'thus enabling the power amplifier 32 to anode modulate the oscillator T, when the system is actuated by the microhone.

The bias resistor 43, is shorted out through the contacts 56 and 54 on the relay switch, thus making the variable resistor 42 the only bias resistor. The variable resistor 42 may be used to control the strength of oscillation, and thereby the magnitude of the transmitted signal.

. The coupling circuit, which for reception cou pled the received signal to the oscillator cavity, oscillator signal to the antenna.

The squelch oscillator 30 will be inoperative during transmission, since a large resistor 45 is inserted in its cathode circuit.

What is claimed is: 1. In combination, an ultra high frequency oscillator having a cavityresonator as .a fre;-

quency determining element, a switch and a; relay having contactsunder control of said switch, and means including said contacts for "causing said oscillator and associated circuit to operate either as a transmitter or as a detector of signals, and a tuning element for said cavity resonaton under control of the winding of said relay for automatically changing the tuning of :said cavity resonator by a predetermined amount when the function of said oscillator is changed, said tuning element comprising a movable insert adapted substantially to bridge opposite walls of said resonator.

2. In combination, an ultra high frequency oscillator havinga cavity resonator as a frequency determining element, a switch and a relay having contacts under control of said switch, and means including said contacts for causing said oscillator and associated circuit to operate either as a transmitter or as a detector of signals and a tuning element for said cavity resonator under "control of the winding of said relay for automatically changing the tuning of said cavity .resonator by a predetermined amount when the function of said oscillator is changed, saidv tuning element comprising a movable insert adapted for insertion in said cavity resonator at a .location where the voltage gradient acrosssaid resonator is relatively large. I

3. In combination, an ultra high frequency oscillator having a cavity resonator as a frequency, determining element, circuit means including a switch and a relay under control of said switch for operating said oscillator eitheras a transmitter or as a detector of'signals, and a tuning element for said cavity resonator under control of the Winding of said relay for auto,-

matically changing the tuning of said cavity resonator by a predetermined amount when the function of said oscillator is changed, said tuning element comprising a movable insert adapted for insertion in said cavity resonator, said insertbeing in the form of an insulating plug bridging said resonator and surrounding a metallic rod of smaller size and shorter length.

4. In combination, a cavity resonator, and

.means for tuning said resonator comprising a slidably movable insert bridging two walls of said resonator at a location where the voltage gradient is large for changing the frequency of operation, said insert comprising an insulation plug surrounding a metallic rod of shorter length, the length of said metallic rod being slightly longer than the distance betweensaid two walls of said resonator, and a solenoid for moving said insert between two fixed positions.

5. An ultra high frequency transceiver comprising alighthouse type of vacuum tube oscillator having a cavity resonatoras a frequency determining element, a switch and a relay hav; ing contacts under control of saidswitch, means including said contactsifor causing said oscillator and associated circuit to operate either as a transmitter or as a super-regenerative detector, and a movable insert for said cavity resonator under control of the winding of said relay for automatically changing the tuning of said cavity resonator by a predetermined amount when the function of said oscillator is changed, said insert bridgingtwo opposite walls of said resonator at a location where the voltagegradient across the resonator is relatively large, said insert including a metallic element which is longer than the distance between said two opposite walls.

6. An ultra high frequency transceiver comprising a lighthouse type of vacuum tube oscillator operating to generate oscillations of the order of thousands of megacycles, said tube having physically spaced parallel grid and anode electrode terminals and a cathode, a cavity resonator having oppositely disposed substantially parallel Walls, an aperture in at least one of said walls for enabling the anode terminal end of said vacuum tube to enter the interior of said resonator, means coupling one of said walls to said grid electrode terminal, means coupling the other of said walls to said anode electrode terminal, a coaxial line resonator located externally of said cavity resonator and coupled to the cathode and the grid terminal of said vacuum tube, a switch and circuit elements associated therewith including a relay for conditioning said vacuum tube oscillator to function either as a transmitter oscillator or as a super-regenerative detector, an insert comprising an insulation plug surroundin a metallic rod movable between oppositely disposed walls of said cavity resonator for changing the resonant frequency of said cavity resonator, said relay including a solenoid responsive to the operation of said switch for moving said insert between two predetermined positions.

7. An ultra high frequency transceiver comprising a lighthouse type of vacuum tube oscillator operating to generate oscillations of the order of thousands of megacycles, said tube having physically spaced parallel grid and anode electrode terminals and a cathode, a cavity resonator having oppositely disposed substantially parallel walls, an aperture in at least one of said walls for enabling the anode terminal end of said vacuum tube to enter the interior of said resonator, means coupling one of said Walls to said grid electrode terminal, means coupling the other of said walls to said anode electrode terminal, a coaxial line resonator located externally of said cavity resonator and coupled to the cathode and the grid terminal of said vacuum tube, a switch and circuit elements including a relay having contacts associated therewith and means including said contacts for conditioning said vacuum tube oscillator and its associated circuit to function either as a transmitter oscillator or as a super-regenerative detector, a movable metallic rod for said cavity resonator supported between said same oppositely disposed walls of said cavity resonator for changing the resonant frequency of said cavity resonator, said metallic rod having a length slightly greater than the distance between said walls, said relay including a solenoid responsive to the operation of said switch for moving said insert between two predetermined positions.

8. The combination with an ultra high frequency oscillator having a resonant chamber for controlling the frequency of said oscillator, and a movable insert for said chamber, of means for operating said oscillator either as a transmitter or as a detector of signals, a relay having contacts under control of said first means for changing the position of said insert, said contacts and associated circuit means serving to change the operating condition of said combination as either a transmitter or a detector, and adjustable means for controlling the frequency of reception both above and belowthe frequency of transmission.

PAUL F. G. HOLST. LOREN R. KIRKWOOD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,018,569 Pettengill et a1 Oct. 22, 1935 2,259,690 Hansen et al Oct. 21, 1941 2,284,405 McArthur May 26, 1942 2,415,242 Hershberger Feb. 4, 1947 2,416,794 Crosby Mar. 4, 1947 2,417,542 Carter Mar. 18, 1947 2,425,495 Trevor Aug. 12, 1947 2,452,601 Ranger Nov. 2, 1948 FOREIGN PATENTS Number Country Date 453,733 Great Britain Sept. 17, 1936 470,366 Great Britain Aug. 13, 1937 512,121 Great Britain Aug. 29, 1939 550,774 Great Britain Jan. 25, 1943 

